1. Field of the Invention
The present invention relates to an improved intramedullary nail and method for stabilizing fractures of the femur. More specifically, the present invention relates to a surgical interlocking intramedullary nail including an interlocking screw assembly for immobilization of distal femur parts involved in fractures occurring in the condylar and supracondylar portions of the femur.
2. Description of the Prior Art
It is known that bone parts or fragments involved in fractures of the femur are difficult to stabilize satisfactorily. Since the femur functions as a weight bearing bone, the femoral fractures often take longer to heal and there is potential for greater complications in setting the fracture than in non-weight bearing bones. Furthermore, it is well understood that patients that remain inactive following surgery have an increase in the risk of serious complications including the development of blood clots and pneumonia. Therefore after stabilizing a femoral fracture, early mobilization of a patient is necessary so that the femur will heal quickly, with stronger repair and less likelihood of complications.
In treating a femoral fracture, it is standard practice to use a fixation device adapted to facilitate recovery of the fractured bone. The fixation device provides immobilization of the bone fragments and stabilization of the fractured femur, thus providing earlier mobilization and weight bearing of a patient. The fixation device is attached to or inserted into the femur and cooperates with the bone fragments and the femoral shaft to stabilize the bone. As the bone heals, the fixation device allows the bone fragments to compress into each other so the fragments grow together to restore the bone.
Two prevalent types of femoral fractures are supracondylar or xe2x80x9cT-typexe2x80x9d condylar fractures about the distal femur. A number of different fixation devices, both external and implantable, have been devised for fixation of supracondylar and condylar fractures. In the past, treatment of condylar or supracondylar fractures consisted of stabilizing the bone portions with plates and screws. However, in using plates and screws, invasive surgery is required and includes considerable dissection of the thigh in order to expose the fracture so as to attach the plates and screws. The resultant devasculariztion of the distal portion of the femur has lead to a high frequency of complications of delayed union of the bone sections, osseous fracture and infection. Additionally, due to the muscular stresses in the region of the condylus and supracondylus, the treatment may involve undesirable post-operative procedures and complications including the bending or breaking of the plates, loosening of the screws and migration of the femoral shaft.
Recently, intramedullary (IM) nailing has become a standard procedure for treating supracondylar and condylar fractures. In its basic form, IM nailing consists of driving a rod-like nail into the intramedullary bone canal of the femur to stabilize transverse fractures of the femur. However, such IM nails often fall short to provide effective fixation or immobilization for supracondylar and condylar fractures since they fail to sufficiently compress bone fragments. Improvements have been made on IM nails to further stabilize the bone fragments by introducing interlocking cross-bolts or screws through the nail that are fixed on both sides of the fracture.
Despite their advantages over plate and screw fixation devices, there are still complications that arise with interlocking IM nails. One difficulty is that the screws may loosen, creating a decrease in screw fixation which results in screw toggling, or in a worst case scenario, complete screwing out of the nail. Another difficulty results from the oblique position of the condyles with respect to the shaft of the femur. Since the fixation of the screws is often transverse to the femoral shaft, the screws do not extend through the major mass of the cancellous bone of each condylus. Furthermore, the sizes of many current screws used with the IM nails do not achieve sufficient purchase in the bone. Stabilizing the fracture is further compounded by the fact that the bone is often of poorer quality.
Known IM nails have been designed for treatment of condylar and supracondylar fractures. For example, U.S. Pat. No. 5,779,705 issued to Matthews and U.S. Pat. No. 6,010,505 Asche et al., which are herein incorporated by reference in their entirety, each disclose an intramedullary device having an IM nail and interlocking bolts or screws to grip and stabilize the femoral condyles with respect to the femoral shaft. The disclosures of the references are considered to establish the state art for condylus and supracondylus IM nails. Each of the devices disclosed thereby addresses the desirability of compression in the treatment of femoral fractures and emphasizes compression of the condyles with respect to the femoral shaft.
Matthews discloses an intramedullary nail incorporating a Cruciate arrangement of two obliquely crossing locking bolts such that each condyle of the femur is gripped by an individual bolt. The Cruciate or staggered/crossed configuration of holes permits two distal locking bolts to be inserted.
Asche et al. discloses a supracondylar bone nail that has an elongated shank with two bends. The first bend begins at a distance from the distal end of about a quarter or a third of the length of the nail at an angle of about 8xc2x0. The second bend begins in the last third of the nail length if looking from the distal end and has an angle of approximately 3xc2x0. The nail includes transverse bores in the distal and proximal end which are adapted to accommodate screws.
Although effective results have been achieved with the above noted IM nails, problems of internal fixation still persist. Therefore, it is desirable to modify an IM nail so as to achieve greater internal fixation of the condyles and mitigate screw loosening and toggling.
To meet the above noted desires, it is an object of the present invention to provide an interlocking intramedullary nail for fixation of the distal femur which overcomes certain disadvantages of the prior art devices while maintaining their advantages. The present invention provides an interlocking intramedullary nail that aims to achieve greater fixation and immobilization of condylus and supracondylus fractures of the femur.
According to one embodiment of the present invention, the interlocking intramedullary nail comprises an intramedullary nail, a first lag screw, a second lag screw and a locking screw, all being adapted to accommodate one another. The nail is configured to be inserted from a distal end of the femur below the condylus and has a distal end with a transverse bore extending therethrough. The first lag screw has a distal end with a cylindrical first portion and an axial through hole. The first lag screw is arranged to be inserted into one end of the transverse bore. The second lag screw has an axial through hole and is adapted to receive the cylindrical portion of the first lag screw at another end of the transverse bore. The locking screw is adapted to be inserted into the axial through hole of the second lag screw so as to thread onto the first lag screw and the second lag screw.
According to a second embodiment, the interlocking intramedullary nail has at least one transverse distal bore that is angled with respect to a longitudinal axis of the nail such that the first and second lag screws extend obliquely from the intramedullary nail.
According to another variant of the invention, the first lag screw and the second lag screw each may include a major external thread diameter having a taper. Further, according to yet another variant of the invention, the first lag screw and the second lag screw each may include a minor external thread having a taper. Still further, according to another embodiment of the invention, the first lag screw and the second lag screw each may include a major external thread diameter having a taper and a minor external thread diameter having a taper.
For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description, taken in conjunction with the accompanying drawings describing the preferred embodiments thereof.